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Sinnerite, Cu6As4S9, from the lengenbach quarry, Binn Valley, Switzerland: Description and re-investigation of the crystal structure

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We have characterized the crystal structure of sinnerite, Cu6As4S9, a rare sulfosalt mineral from the ores of the Lengenbach quarry, Binn Valley, Canton Valais, Switzerland, by single-crystal X-ray diffraction and chemical analysis. We found sinnerite to be structurally identical to synthetic Cu6As4S9. It is triclinic, space group P1, with cell parameters: a 9.103(2), b 9.860(3), c 9.111(2) angstrom, alpha 90.27(2), beta 109.53(2), gamma 107.58(2)degrees, V 729.6(4) angstrom(3), and Z = 2. Semi-quantitative SEM-EDS analyses confirmed the Cu6As4S9 stoichiometry. The crystal structure of an untwinned crystal has been refined to R-1 = 5.45%. It consists of a sphalerite substructure with 2/5 of the tetrahedra replaced by AsS3 pyramids; four pyramids form As4S12 clusters around the vacant anion positions of the sphalerite archetype. These pyramids are linked into twisted and branched chain-like structures with compositions As3S7 and As5S11. The chains are linked by CuS4 tetrahedra. Packing of these chains results in the OD (order-disorder) character of the sinnerite structure.
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... The Ag2 position dominated by Cu in eckerite shows a quasi-tetrahedral coordination with a mean bond distance of 2.542 Å compared to 2.674 Å in Cu-free xanthoconite (Engel and Nowacki, 1968). The ordering of copper mainly at (Karanovic et al., 2002); luzonite (Pfitzner and Bernert, 2004); sinnerite (Bindi et al., 2013)]. The shortest AgÀAg contact in the eckerite structure is Ag1ÀAg2 at 2.835 Å , slightly shorter than that found in fcc Ag metal (2.889 Å ; Suh et al., 1988). ...
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Faszination Lengenbach Abbau-ForschungMineralien International Tables for X-ray Crystallography The Netherlands
As6-S1 2.33(3) Cu8-S3 2.28(3) As6-S7 2.40(3) Cu8-S4 2.31(2) As6-S11 2.54(3) Cu8-S12 2.34(3) Cu8-S10 2.45(3) As7-S10 2.27(3) As7-S5 2.30(3) Cu9-S9 2.20(3) As7-S18 2.36(3) Cu9-S4 2.24(3) Cu9-S2 2.31(3) As8-S4 2.20(3) Cu9-S13 2.36(3) As8-S14 2.25(3) As8-S8 2.34(3) Cu10-S5 2.22(3) Cu10-S11 2.38(3) Cu1-S16 2.20(3) Cu10-S4 2.42(3) Cu1-S6 2.27(3) Cu10-S17 2.40(3) Cu1-S18 2.30(3) Cu1-S14 2.47(3) Cu11-S9 2.16(3) Cu11-S18 2.20(3) Cu2-S18 2.29(3) Cu11-S17 2.21(3) Cu2-S15 2.34(3) Cu11-S3 2.33(3) Cu2-S1 2.39(3) Cu2-S12 2.44(3) Cu12-S3 2.11(3) Cu12-S15 2.22(3) Cu3-S1 2.15(3) Cu12-S7 2.28(3) Cu3-S14 2.30(3) Cu12-S16 2.33(3) Cu3-S17 2.31(3) Cu3-S2 2.47(3) graEsEr, s., cannon, r., drEchsLEr, E., rabEr, t., & roth, p. (2008) Faszination Lengenbach Abbau-ForschungMineralien 1958-2008. Kristallographik Verlag, Achberg, 192p. ibErs, J.a. & hamiLton, w.c., Eds. (1974) International Tables for X-ray Crystallography, Volume IV. Kynoch Press, Dordrecht, The Netherlands, 366p.
Studies of the sulfosalts of copper. II. The crystallography and composition of sinnerite, Cu 6 As 4 S 9
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Faszination Lengenbach Abbau-Forschung-Mineralien
• S Graeser
• Cannon
• E Drechsler
• P Roth
graEsEr, s., cannon, r., drEchsLEr, E., rabEr, t., & roth, p. (2008) Faszination Lengenbach Abbau-Forschung-Mineralien 1958-2008. Kristallographik Verlag, Achberg, 192p. ibErs, J.a. & hamiLton, w.c., Eds. (1974) International Tables for X-ray Crystallography, Volume IV. Kynoch Press, Dordrecht, The Netherlands, 366p.